1. Field of the Invention
The invention relates to a pressure cylinder for a printing machine with air-conditioning and oil lubrication of the cylinder.
2. Description of Related Art
Printing machines employ deformable pressure cylinders, that is to say cylinders with a variable curvature, consisting essentially of a casing which is equipped on its outside with a rubber coating and which is carried by a central supporting shaft, with ball bearings interposed. The supporting shaft is mounted in the side stands of the printing machine.
Pressure cylinders of this type, which are used, for example, for the accurate guidance of the paper web or for pressing the paper web against the compression cylinder, rotate at a considerable speed. For this reason, for the reliable operation of the pressure cylinders it is necessary to provide a perfect lubrication of the ball bearings. It has also proven advantageous if the quantity of heat generated in the pressure cylinders is conveyed continuously away from the cylinder and from the rotating bearings.
In known pressure cylinders, the ball bearings are mostly lubricated by means of a charge of grease, but this lubrication is not without its problems. In the known pressure cylinders, there have hitherto been no means making it possible to air-condition the pressure cylinder in thermal terms, that is to say there have been no known means by which the heat generated could actually be dissipated from the pressure cylinder, especially from the ball bearings of the cylinder, that is to say at points where the cylinder experiences the highest thermal stress. This leads to considerable local heating of the pressure cylinder, especially in the vicinity of the supporting bearings. This accumulation of heat leads, in turn, to a pronounced thermal expansion of the outer cylinder casing, this resulting in an undesirable increase in diameter of the pressure cylinder, particularly in the vicinity of the supporting bearings, thereby entailing dimensional deviations which themselves give rise to printing errors.